Octane requirements for my 2.1 liter waterboxer

[beebrew]

I know VW asks for 91 octane gas for my 88. With fuel prices rising, and high octane gas being a premium, I feel the a temptation to try 89 octane fuel. I am aware if the octane is too low, pre-ignition can do harm. My question is how close are the theory and practice of this octane requirement? Are there folks out there doing this without issues? If so, did they retard the spark or take other measures to make things happy? My gut says be careful, my wallet says this gas is too expensive! Thanks for any feedback. It is always fun hearing other peoples views. Looking forward to some LIMBO events this summer.
Guy K  :wink:

[Vanagonjr]

I was kinda of wondering the same thing.  On cars with knock sensors, there is not much worry running lower octane, but the Vanagon certainly doesn't have one!

[Stanagon]

Boston Bob has always told me to run premium in the air-cooled Vanagon. I'll ask him what he is running in his fleet of water boxers. Likely it's low test with the prices these days.

Whatever you run, keep careful track of mpg, it may be better with  higher octane and negate some of the price premium.

[beebrew]

I like the idea of a knock sensor. My understanding is when incorporated in a vehicle, they are configured to have the distributor automatically retard the spark. That would be cool. I looked for after market conversions, but found nothing.  Meanwhile the octane questions still looms!

[mark & carol]

i just use 87.at 3.95 a gallon

[beebrew]

When running the 87 octane, does it ever knock pulling hills? Knocking sounds like dry beans being shook in a tin can.

[MrLiMBO]

i just use 87.at 3.95 a gallon

I've always run regular 87 octane gas in everything I own. Air-cooled to wasserboxers.  Never had any trouble.  My 90 Jetta is the only car with a knock sensor.  The only car I would notice some light knocking was the Eurovan.  It only happened when I was towing in the summer with the A/C on and it was like 85 outside.  Otherwise, it was fine.  At 4.30 a gallon for super, you don't see that much gain for your money.   It might be cheaper to buy some octane booster from the autoparts store.

[volksbulli]

I'm truly baffled by how little people actually know about the different octane ratings. The higher the octane the slower the air fuel mixture burns. This is most important in High compression Engines where the risk of pre-ignition and detonation is high. Most Vanagon motors are not race engines or anything I do realize they have marginally higher compression than that of their air cooled counter parts. But in all seriousness if you are  running Ultra 94 octane (if Sunoco has it anymore) in a vehicle you are not making it run better, you are making it run with less power. This is because you are putting a slower burning fuel into an engine that was designed to run a faster burning fuel.

  Look at muscle cars from the 60's and very early 70's (pre-emissions) They all had high Compression engines and the had a lot better high octane gas then. Take for example a 64' Ford Galaxie 500, they had a 390ci engine with 11.5 to 1 compression ratio which made 390hp on premium fuel. That same motor in the mid 70's with emission regulation and a 7.0 to 1 compression ratio made 190-200 hp if you were lucky on regular gas.

 Not to be ripping on anyone but octane boosters are over rated, if you know how the octane system works.
 
 I've run regular gas in all my VW's with no issues for years, most of knocking and pinging issues come down to timing and motors being out of tune.